The proposed research will study the mechanism by which araC gene protein of the L-arabinose operon of Escherichia coli positively and negatively regulates the operon. This will be done with in vivo studies on wild type and mutant cells, and with in vitro studies with purified components of the system--DNA, araC protein polymerase, and cyclic AMP binding protein. The studies involve the purification and study of DNA fragments containing the regulatory region of the arabinose operon and the proteins involved in the regulation of the operon. Studies will include high magnification electron microscopy, DNA sequencing, and physiological studies. BIBLIOGRAPHIC REFERENCES: Location in Bacteriophage Lambda DNA of Cleavage Sites of the Site-Specific Endonuclease from Bacillus amyloliquefaciens H. D.M. Haggerty and R.F. Schleif, J. of Virology, 18, 659-663 (1976). Electron Microscopy of Gene Regulation: The L-arabinose Operon, J. Hirsh and R. Schleif, Proc. Natl. Acad. Sci. USA, 73, 1518-1522 (1976).